1. Field of the Invention
The invention relates to television signals.
2. Related Art
In displaying television signals including detailed information, such as text (or other relatively sharp or small images, including icons, chyrons, or graphical line art), it is desirable for the displayed images to be displayed sharply but without visual artifacts resulting from finite-size pixels or from Y/C separation. In the known art anti-aliasing is one method for reducing visual artifacts when the image is small relative to the available pixels.
One problem in the known art is selection of a background color with respect to which to perform anti-aliasing. In particular, performing anti-aliasing with respect to a single color, namely the constant background color is more effective than when the background includes a range of colors. This problem is exacerbated when the background is a dynamically changing image, such as a slide show, another animated graphical display, or a video display such as broadcast television.
Accordingly, it would be desirable to provide an improved method and system for presenting television signals, including anti-aliasing of text with respect to a background. This advantage is achieved in an embodiment of the invention in which the background color is determined relatively locally, and text or other graphics overlaid on that background are anti-aliased with respect to each relatively local background color.
The invention provides an improved method and system for presenting television signals, including anti-aliasing of text with respect to a background. The background color may be determined relatively locally for each element to be anti-aliased, and text or other graphics overlaid on that background are anti-aliased with respect to each relatively local background color. Therefore the invention comprises a background color detector for dynamically determining the background colors of displayed images or text and some form of anti-aliasing processor for anti-aliasing the edges of those displayed images or text based upon the dynamically determined background colors.
Also, in an embodiment of the invention, anti-aliasing is used to blur text and graphics more vertically than horizontally to reduce flicker from interlaced display. Further, in an embodiment of the invention, anti-aliasing can blur chrominance more than luminance to further reduce cross-chrominance beyond the reduction already achieved by anti-aliasing.